The long-term goal of this multicenter PPG is to define the mechanisms responsible for the malignant hyperthermia syndrome caused by mutations in RyR1 and Cav1.1 as well as leveraging new discovery of other gene linkage in humans. The scope of investigations will range from extensive phenotyping of MH mice, studies of Ca2+ and Na+ homeostasis in muscle from MH mice and MHS humans and the importance of TRPCs (Project 1), studies of RyRI function, how MHS mutations cause posttranslational modifications, mitochondrial adaptations and metabolic abnormalities (Project 2), and how disruption of the normal interactions between RyR1 and CaVI.1 lead to Ca2+ dysregulation in MH susceptible animals and patients (Project 3), and the influence of MH mutations on the cellular physiology of muscle (Projects 1, 2, & 3). Our research in the previous funding period has led to a unified general hypothesis applicable to any and all MH mutations: MH is caused by primary structural changes in RyRI, or by structural changes in RyRI induced indirectly by a mutation in Cavl.1 or another protein closely associated with RyR1 (as demonstrated by an MH like phenotype in Casq1 null mice). A transformative concept to be investigated by all PPG participants is that a defect in Cav1.1 f-RyR1 bidirectional signaling is a common convergent pathway leading to all MH susceptibility and progressive muscle damage. The focus of this program is tightly linked. All 3 Projects will: 1. Examine the relationship between gender and MH penetrance, 2. Validate the pathology in mouse models in human muscle. 3. Determine if the sequelae of MHS mutations can be reduced or prevented by genetic/pharmacological manipulations that decrease sarcolemmal Ca2+ entry, reduce RyR1 leak, increase SR Ca2+ load or scavenge lipid peroxides resulting from ROS production. 4. Using discovery from Core C establish the mechanisms by which newly discovered mutations not in RyR1 or Cav1.1 disrupt the normal bidirectional signaling between RyR1 and the DHPR leading to a common cascade causing MHS and its associated pathology, each using their unique expertise. In this way we assure that the outcome will be that the whole of this Program is greater than the sum of the individual parts.